Field
The present disclosure relates generally to medical devices, and specifically to surgical instruments and methods for performing spinal procedures.
Background
The spine is formed of a column of vertebra that extends between the cranium and pelvis. The three major sections of the spine are known as the cervical, thoracic and lumbar regions. There are 7 cervical vertebrae (C1-C7), 12 thoracic vertebrae (T1-T12), and 5 lumbar vertebrae (L1-L5), with each of the 24 vertebrae being separated from each other by an intervertebral disc. A series of about 9 fused vertebrae extend from the lumbar region of the spine and make up the sacral and coccygeal regions of the vertebral column. The natural curvature of the spine includes a combination of lordosis and kyphosis. Specifically, the cervical and lumbar portions of the spine exhibit a natural lordotic curvature, meaning that they are set in a curve that is anteriorly convex (and posteriorly concave). The thoracic portion of the spine has a naturally kyphotic curvature, meaning that it is set in a curve that is anteriorly concave (and posteriorly convex).
The main functions of the spine are to provide skeletal support and protect the spinal cord. Even slight disruptions to either the intervertebral discs or vertebrae can result in serious discomfort as well as compression of nerve fibers either within the spinal cord or extending from the spinal cord. If a disruption to the spine becomes severe enough, severe pain, disability and damage to a nerve or part of the spinal cord may occur and can result in partial to total loss of bodily functions (e.g., walking, talking, breathing, etc.). Therefore, it is of great interest and concern to be able to both correct and prevent any ailments of the spine.
Fixation systems are often surgically implanted to stabilize or immobilize a portion of the spine. They are generally utilized during spinal fusion procedures to immobilize the applicable vertebrae until bone growth occurs to effect the fusion and/or to correct vertebral alignment issues. Fixation systems often use a combination of rods, plates, pedicle screws, and bone hooks to attach a fixation construct to the affected vertebrae. The configuration required for each procedure and patient varies due to the ailment being treated, the specific method of treatment (e.g. surgical approach, etc.) and the patient's specific anatomical characteristics. One of the most common methods for achieving the desired immobilization is through the application of bone anchors (pedicle screws or hooks) that are then connected by rigid rods locked to each bone anchor. Pedicle screws, when used, are most often introduced into the pedicles associated with the respective vertebra to be fixed. Hooks, likewise, are attached with the pedicles associated with the respective vertebra to be fixed. Hook implants are used in order to provide alternative fixation to pedicle screws. Traditional hook implants are often placed in a caudal orientation at the upper instrumented vertebrae. In addition, hooks may be implemented when a pedicle is too small for a pedicle screw. Pedicle screws/hooks generally include an anchor component and a rod-housing component (or “tulip”) that is coupled to the anchor component.
Traditional hooks rely upon caudal trajectory to maintain purchase on the vertebral body. As a result, this often requires the surgeon to violate and/or reset the superior facet joint. Alternatively, hook/claw constructs may be implemented by the surgeon to achieve enhanced purchase when compared to a single hook. The hook/claw construct involves placing two hooks, one facing caudal and the other cephalad, on opposing sides of the vertebral body. However, this once again requires the surgeon to violate the superior facet joint. Finally, hook with screw implants may be implemented to increase the purchase of a hook to the vertebral bone. The hook with screw may be placed in either the caudal or cephalad orientations depending on the surgical goals of the doctor. However, multiple steps are needed to implant the hook with screw, and often the screw must be inserted before the rod placement is normalized.